The present invention relates to a dispenser for dispensing a low cross-linking-density gel used to connect optical fibers, and an optical fiber connector for connecting end faces of optical fibers.
An optical fiber connector, a fixed connecting device, a light combining/splitting device or like device has been generally used to connect end faces of optical fibers.
A mechanical contact method is mainly used to connect end faces of optical fibers in an optical fiber connector. According to this mechanical contact method, ferrules are respectively fitted on cores of both optical fibers and are inserted into fitting holes, which are formed in the opposite side surfaces of a connector main body to communicate with each other in linear alignment with each other, from the opposite sides of the connector main body, and the end faces of the two cores having the ferrules fitted therearound are fixed in abutment against each other to be connected with each other.
Besides the above mechanical contact method, for example, there have been proposed the use of a lens as an optical conductor at a joint portion and the use of a matching oil in the optical fiber connector as disclosed in Japanese Unexamined Patent Publications No. 56-110912 and No. 56-81807, respectively.
On the other hand, matching oil, matching grease, epoxy resin or the like is used as an optical conductor for the connection of optical fibers in a fixed connecting device or light combining/splitting device.
It is basically required in the connection of the optical fibers to maximally eliminate the diffusion of light at the joint portion of the two end faces.
However, according to the method for mechanically bringing the end faces of the optical fibers into contact with each other, an air layer is inevitably present between the end faces due to its mechanical construction. Since this air layer and the cores of the optical fibers have different refractive indices, light is diffused due to a difference in refractive index, resulting in a loss of light.
An arrangement of an optical conductor between the end faces has been proposed and put into practice in order to eliminate the air layer and prevent the loss of light.
However, the prior art method using a lens as the optical conductor necessitates a complicated construction and the use of a large-sized apparatus and has a problem in reliability during the attachment and detachment of the optical fibers. Thus, this method has low industrial applicability.
The prior art method using matching oil as the optical conductor has problems of flow-out and oxidation of the oil resulting from increase and decrease of temperature, and a problem of a short life. Particularly, if silicone oil is used as the matching oil, it is difficult to prevent the silicone oil from flowing out due to its creeping characteristic. Thus, the use of the matching oil compels an exchange of oil after a certain period of time and, therefore, has low industrial applicability.
On the other hand, the method using grease as the optical conductor has been proposed in order to avoid the above problems of flow-out and oxidation of oil. Grease can certainly avoid an undesirable event of flow-out due to its high viscosity, but cannot avoid problems of changes in characteristics caused by temperature and a difference in refractive index between a thickening agent and a composition and has a lower light transmittance as compared to the case where the matching oil is used. Further, grease has a fatal problem of being unable to restore (eliminate) air bubbles produced by a displacement of the two end faces at the joint portion. Therefore, grease also has low industrial applicability.
According to the prior art method using an epoxy resin as the optical conductor, the epoxy resin is cured by heating or air-cured, and displays a satisfactory performance over a long period of time. However, this method has an unavoidable problem of coloring due to oxidation. In view of operability, mixing of a curing agent, removal of air bubbles, curing by heating, etc. are necessary during the manufacturing process. Further, in the case of defective connection of the end faces, the optical fibers have to be thrown away and the whole process has to be resumed from the beginning. This method is used despite its poor yield, but has low industrial applicability.
On the other hand, the inventors of the present application invented the filling of a gelatinous material having a refractive index similar to that of the cores of the optical fibers. However, there is no dispenser for dispensing a very tiny predetermined amount of this gelatinous material. Thus, despite the finding of the inventive gelatinous material, it cannot be dispensed by a predetermined amount into an optical conductor. Therefore, there is a demand for an improved dispenser.
The present invention was developed in view of the above situation, and a main object thereof is to provide a dispenser which can dispense a low cross-linking-density gel used to join end faces of optical fibers.
It is another object of the present invention to provide an optical fiber connector which can join end faces of optical fibers while effectively suppressing the diffusion of light despite its simple construction.
It is still another object of the present invention to provide an optical fiber connector which can suppress the diffusion of light by maintaining its working performance over a long period of time.
In order to solve the aforementioned problems and accomplish the above objects, a dispenser, comprising;
an outer tube having one end formed with an insertion hole and the other end being open, and extending straight along a specified longitudinal axis,
a syringe having one end to which a nozzle insertable into the insertion hole is attached, and being adapted to contain a low cross-linking-density gel which has been produced therein,
a piston head slidably provided in the syringe along a longitudinal direction for sealing the low cross-linking-density gel therein, and
a dispensing means mounted on the outer tube for coming into contact with the piston head through the open other end of the syringe to push it, thereby dispensing the low crosslinking-density gel in the syringe through the nozzle.
In the inventive dispenser, a cap for sealing the inside of the syringe is mounted on the syringe instead of the nozzle when the low cross-linking-density gel is produced in the syringe.
In the inventive dispenser, the piston head seals the inside of the syringe as a sealing packing when the low cross-linking-density gel is produced in the syringe.
In the inventive dispenser, the dispensing means is so constructed as to dispense a predetermined amount of the low cross-linking-density gel.
In the inventive dispenser, the dispensing means includes:
a piston rod which is movably mounted on the outer tube along the longitudinal direction and whose leading end can be brought into contact with the piston head,
a first engaging means provided between the piston rod and the outer tube for moving the piston rod along the longitudinal direction as the piston rod is rotated,
a rotary tube rotatably mounted on the outer surface for covering the piston rod,
a second engaging means which is provided between the rotary tube and the piston rod and is engaged to rotate the piston rod together as the rotary tube is rotated and permit the movement of the piston rod along the longitudinal direction, and
a rotation locking means for locking the rotary tube such that the rotary tube is rotatable by a specified angle every time it is turned.
In the inventive dispenser, the rotary tube is transparent so that the inside thereof is visible from outside.
In the inventive dispenser, the outer circumferential surface of the rotary tube is so graduated as to indicate a remaining amount of the low cross-linking-density gal in the syringe,
In the inventive dispenser, the outer tube is integrally mounted with a mount block having a center hole which penetrates the mount block along its center axis, the piston rod is slidably inserted into the center hole; and the first engaging means includes a lead groove formed on the outer surface of the piston rod and a lead groove formed in the inner surface of the center hole; the two lead grooves being meshed with each other; and the piston rod is moved along the longitudinal direction as being rotated about the center axis by the spiral engagement.
In the inventive dispenser, the second engaging means includes at least one elongated projection formed on the piston rod and extending along the longitudinal direction and at least one spline groove formed in the inner surface of the rotary tube and extending along the longitudinal direction, the at least one projection and the at least one spline groove being engaged with each other.
In the inventive dispenser, the rotary tube is so mounted as to cover the outer circumferential surface of the mount block, and the rotation locking means includes a plurality of recesses formed in the outer circumferential surface of the mount block and circumferentially arranged at equal intervals, and a locking ring mounted on the rotary tube and selectively elastically engageable with one of the plurality of recesses.
The invention is also directed to an optical fiber connector, comprising:
an adapter formed with a center through hole extending along its center longitudinal axis, fittings bearing optical fibers from which cores project by specified distances being mountable into the through hole from the opposite sides such that the cores are aligned with each other, and
an optical conductor arranged in the center through hole and including a sleeve fitted into the through hole and a low cross-linking-density gel filled in the sleeve,
wherein the cores are inserted into the low cross-linking-density gel from the opposite sides such that the end faces thereof are opposed to each other.
In the inventive optical fiber connector, fixing nuts for fixing the fittings mounted into the adapter to the adapter are further provided.
In the inventive optical fiber connector, the sleeve is made of a synthetic resin which is stable against the low cross-linking-density gel filled therein.
In the inventive optical fiber connector, the low cross-linking-density gel is produced by causing a flexible silicone gel material adjusted to have a specified refractive index to undergo an addition reaction in a binding region where cross-linking density is low.
In the inventive optical fiber connector, the specified refractive index is substantially equal to that of the cores of the optical fibers to be connected.
In the optical fiber connector, the flexible silicone gel material is a polyorganosiloxane having vinyl groups at its ends and a polyorganosiloxane having covalently bound hydrogen atoms.
In the inventive optical fiber connector, the addition reaction is performed by heating.
In the inventive optical fiber connector, the low cross-linking-density gel is produced in a clean room.
A first requirement for a material used for the connection of end faces of optical fibers is that it is easily deformable like an elastic material during the connection, can be formed to have an extremely small thickness, is not allowed to flow like usual viscous matter or liquid, and does not contain in its texture anything, which hinders the propagation of light, such as filler, dust or air bubbles having different refractive indices.
A second requirement for this material is that it is resistant to changes in outer environments such as temperature, humidity, pressure and vibrations.
A third requirement for this material is that it does not permit dust, vapor, water and the like to intrude thereinto.
A fourth requirement for this material is that it enables an easy connecting operation which can be completed within a short period of time. Specifically, it is required not to increase a temperature for vacuum deaeration and curing in the connecting operation using an epoxy resin.
The inventors of the present application studied the structures of various elastic materials and viscous materials during the development of a material which satisfies the above requirements and, in their study, directed their attentions to a macromolecule having a three-dimensional reticulated structure insoluble in a solvent and a gel structure which is a swollen material of such a macromolecule. Consequently, they established a compounding technique according to which a transparent flexible silicone gel material selected as a base material among synthetic gels was gelatinized at a low cross-linking density, thereby forming a low cross-linking-density gel (gel-fluid intermediate) which has a shape retaining property, which is a characteristic of a gelatinous elastic material, while having fluidity.
As a result of repeated devotion and efforts, the inventors completed a compounding technique for producing a low cross-linking-density gel which satisfies all of the aforementioned requirements and found out that this material was optimal as a material used for the connection of end faces of optical fibers. In other words, by merely providing the thus produced low cross-linking-density gel between the end faces of the optical fibers, a loss of light at the joint portion when light was transmitted from one optical fiber to the other could be effectively suppressed and conducting efficiency was remarkably improved.
In this invention, the low cross-linking-density gel is produced as follows.
A transparent flexible silicone gel material having a specified refractive index as a primary agent is caused to undergo an addition reaction in a binding region where cross-linking density is low, with the result that the low cross-linking-density gel having a viscosity and a minimum fluidity can be obtained. As a result of the addition reaction in the binding region where cross-linking density is low, free hydrogen atoms are advantageously absent since a total amount of active hydrogen atoms contribute to the reaction.
In the above addition reaction, a polyorganosiloxane having vinyl groups at its ends, which is a component of the primary agent, and a polyorganosiloxane having covalently bound hydrogen atoms are cross-linked in the presence of a platinum catalyst.
A range of the cross-linking density was specified by an amount of the polyorganosiloxane having covalently bound hydrogen atoms, and a final cross-linking density could be substantially precisely controlled. The cross-linked binding region of the low cross-linking-density gel is in the range of 30% to 10% of the theoretical equivalent of the polyorganosiloxane containing covalently bound hydrogen atoms.
If the gel is produced beyond the above cross-linked binding region, it displays properties more similar to those of an elastic material as the ratio of the polyorganosiloxane having covalently bound hydrogen atoms increases. As a result, the gel loses its fluidity and comes to possess a breakage point, which is not preferable. On the other hand, if the gel is produced below the above cross-linked binding region, the primary agent which is not cross-linked has an increased degree of freedom. As a result, the gel becomes considerably fluid and creeping flow peculiar to silicone takes place, which are both not preferable.
The refractive index of the low cross-linking-density gel can be adjusted to a value substantially equal to those of various optical fibers by adjusting the refractive index of a transparent silicone oligomer as a primary agent in advance. Thus, a loss of light caused by the reflection and diffusion of light due to a difference in refractive index between the cores of the optical fibers to be connected and the low cross-linking-density gel can be suppressed to a minimum level.
As described above, the presence of an air layer at the joint portion when the cores of the optical fibers are connected is not preferable because it brings about a loss of light. Further, a distance between the end faces of the cores is preferably as short as possible. Since the inventive gel can easily flow and be deformed upon being forcibly contacted to thereby securely eliminate an air layer between the end faces of the cores and flatten tiny scratches and polishing streaks, it can suppress a loss of light caused by the presence of the air layer to a minimum level.
The physical properties of such a low cross-linking-density gel and the influences of changes in outer environments thereon can be summarized as follows.
(1) Temperature: wide working temperature range of xe2x88x9240xc2x0 C. to 120xc2x0 C.,
(2) Humidity: moisture absorption into the component is 0%,
(3) Water: water absorption into the component is 0.1% or less,
(4) Dust: dust adheres to the outer surface, but does not permeate into the component,
(5) Pressure: pressurized portion is free to deform,
(6) Vibration: vibration does not cause dilatancy,
(7) Oxidation: unoxidizable and stable against most chemicals,
(8) Flow-out: does not flow out,
(9) Performance: substantially semipermanently maintained.
As can be seen from the above, the low cross-linking-density gel cannot be influenced by any outer environment except a temperature exceeding its own pyrolysis temperature and is most suitably used as an optical conductor and thus is sufficiently useful.
Since the low cross-linking-density gel is used in an extremely narrow area between cores of optical fibers having a diameter of 10 to 50 xcexcm, fine dust or like fine particles should not adhere to the surface thereof. Further, the manufacturing process should not be performed in an environment which permits an access of foreign matters such as dust. Thus, in order to use the low cross-linking-density gel as the optical conductor, a vessel used to produce this gel is desired to be a vessel (syringe) chosen in consideration of the manufacturing process as well as how the gel is actually used. In other words, it is essential that the compounded material filled in the vessel be kept sealed until the gel is actually used after the reaction step.
Conditions required for the above vessel (syringe) are that it has a tubular body which has at least inner circumferential surface thereof formed straight and is open at the opposite ends, one of the open ends has a common mount portion on which a sealing cap used during the manufacturing process and a nozzle used during the application of the gel are selectively mountable since the open end serves as a material injecting opening or a dispensing opening for the low cross-linking-density gel, and a sealing packing, which serves as a receiving portion when raw materials of the low cross-linking-density gel are filled, is movably accommodated in the vessel along its longitudinal direction.
It should be noted that the vessel and the sealing packing can be made of any material provided that this material does not hinder the addition reaction of the silicone.
In order to fill the low cross-linking-density gel described above between the end faces of optical fibers, a dispenser for dispensing a predetermined amount of this gel is necessary. It is essential for the dispenser to have a vessel (syringe) for containing the low cross-linking-density gel to be dispensed, it is not preferable to transfer the low cross-linking-density gel separately formed to this vessel (syringe) in view of the generation of air bubbles. Accordingly, the inventors newly developed a vessel (syringe) having a function as a reaction vessel during the production of the low cross-linking-density gel and a function as a containing vessel for containing the produced low cross-linking-density gel to be dispensed, and assembled this vessel into a dispenser. As a result, a predetermined amount of the low cross-linking-density gel could be applied while satisfying the aforementioned conditions.
Further the optical fibers could be easily connected and the diffusion of light during the connection could be suppressed to a minimum level by filling the aforementioned low cross-linking-density gel into an optical fiber connector.